Many medical devices are constructed of heat-sensitive polymeric materials, glues, glass lenses, and electronic components. Examples of such devices are gastroscopes, colonoscopes, cystoscopes, arthroscopes, transesophageal and vaginal probes, and anesthesia and respiratory therapy equipment. These heat-sensitive devices are very expensive, and thus are typically reused from one patient to another, and cannot be sterilized by steam or dry heat. These heat-sensitive devices are therefore disinfected with the highest levels of liquid chemical disinfectants. High-level disinfectants are able to kill Gram-positive and Gram-negative vegetative bacteria, mycobacteria such as Mycobacterium tuberculosis, fungi, and all types of viruses, with a relatively short exposure, and can also kill high numbers of bacterial spores dried onto surfaces with a much longer exposure time.
The high-level disinfectant chemistries that are available for disinfecting medical devices are glutaraldehydes, other aldehydes such as ortho-phthalaldehyde and formaldehyde, peracetic acid, hypochlorous acid, and chlorine dioxide. These chemistries all have serious limitations as high-level disinfectants. Glutaraldehyde requires about 45 min at 25 C to kill 6 log 10 of mycobacteria, and about 10.0 hrs at 25 C to kill bacterial spores as measured by the Association of Official Analytical Chemists (AOAC) Sporicidal Test 966.04. These are impractical exposure times and temperatures that are often arbitrarily decreased in practice. Glutaraldehyde has a serious odor and sensitization problem that requires special equipment for fume containment and exhaustion. Formaldehyde is a known carcinogen with a noxious odor. Ortho-phthaladehyde has vapors that are relatively odorless, but the vapors can sensitize patients and staff. Some patients and staff have become sensitized to ortho-phthaladehyde, and reacted with anaphylactic shock to repeated exposure to fumes they could not smell. Ortho-phthaladehyde requires about 32 hrs to kill bacterial spores in the AOAC Sporicidal Test 966.04. Ortho-phthaldehyde is relatively insoluble, and thus difficult to rinse from surfaces. The aldehydes may be used and reused for typically 14 to 30 days. Peracetic acid has a sharp odor that must be contained within a machine, and the product is used with a temperature of 50 C to 56 C. The combination of the oxidative peracetic acid used at the relatively high temperature of 50 C to 56 C can be damaging to some glues and polymeric materials. All of the oxidative chemistries such as peracetic acid, hypochlorous acid, and chlorine dioxide are unstable and thus are single- or day-use products.
Thus there is a need for a high-level disinfectant that can disinfect within a practical exposure time and at ambient temperature, with a safe and detectable odor, and with an affordable period of use and reuse for many days. Towards that end my prior U.S. patent was a first step improvement.
Previously we discovered that relatively low concentrations of alcohol enhanced the mycobactericidal activity of glutaraldehyde (U.S. Pat. No. 5,863,547). This patent, however, taught specifically to avoid acetate salt additions (column 2, lines 28-30). Further studies have now discovered that acetate salts in combination with alcohol are necessary to optimize the mycobactericidal activity of glutaraldehyde for a very quick and practical exposure time and temperature such as 10.0 min at 20 C. A further surprising discovery was that the fumes of glutaraldehyde were greatly reduced by the presence of alcohol and acetate salts at the appropriate levels.
With the addition of acetate salts, the pH-value of the un-activated glutaraldehyde solution increased to about 6.5 The stable pH-value for glutaraldehyde is about pH 3.5 to 4.5. Because of the pH-value of 6.5, the glutaraldehyde concentration of the un-activated formulation slowly decreased over a period of about 9 to 12 months of warehouse storage. Thus for example it was necessary to start with a glutaraldehyde concentration of about 3.5% in order to have a glutaraldehyde concentration of at least 2.0% after 12 months of storage, followed by 14 days of use and reuse. Repeated use of the disinfectant inadvertently dilutes the glutaraldehyde concentration as freshly cleaned wet devices carry some water into the disinfectant, and freshly disinfected devices carry some glutaraldehyde to be rinsed away. Also, because of the inadvertent dilution that occurs during 14 days of use and re-use, it is necessary to start with somewhat higher, i.e., up to about 26% alcohol in order to have about 15% alcohol after the inadvertent dilution caused by use and re-use. The acetate salts also must start at the higher concentration of about 8% in order to maintain a minimum effective concentration of about 5% after use and re-use for 14 days. Effective concentration as used here means concentration after about 14 days of use and re-use.
It is a primary objective of the present invention to improve on the formulation of my own prior U.S. Pat. No. 5,863,547 in several important ways. First, to increase the rate of anti-microbial kill; second, to modify the formulation so that it maintains a minimum effective concentration even after use and re-use, for example for 14 days; third, to enhance the rate of kill and the effectiveness of disinfectant by adding acetate salts at levels of from 3% to 8%; and fourth, by surprisingly decreasing the acrid odor of glutaraldehyde fumes by combination of the acetate salts present and the alcohol that is present.
The method or manner of achieving this primary objective as well as others will become apparent from the following description of the invention.